topic Re: Usage of COUNT function in SQL JOINS with/without DISTINCT keyword in SAS Programming

Usage of COUNT function in SQL JOINS with/without DISTINCT keyword

keen_sas — Fri, 01 May 2020 15:32:04 GMT

Have embedded my COMMENTS in the codes, to get an understanding of my requirement.

/*8 observation from Shoes dataset*/
data shoes;
 set sashelp.shoes;
  if region='Canada' and Subsidiary='Montreal';
run ;

/*8 observations from org dataset since same data replicated*/
data org;
 set sashelp.shoes;
 if region='Canada' and Subsidiary='Montreal';
run ;


/*TASK: JOINING both the datasets to get the count of PRODUCT variable and storing the result in CNT variable using COUNT FUNCTION. Since there
are only 8 observation the CNT should also be 8,but because of CARTESIAN product CNT variable is showing 64 . Different results
with different usage of DISTINCT function*/


/*Scenario 1 Not using DISTINCT getting 64 observations in the dataset and CNT varaible
 has 64 observations*/
proc sql noprint;
   create table want1 as select org.region ,shoes.product ,shoes.Subsidiary,shoes.stores,
   count(shoes.product) as cnt
	 	from org as org left join 
       shoes as shoes on org.region = shoes.region	    	     
     group by org.region
     order by org.region;
quit;

/*Scenario 2 using DISTINCT getting 8 observations and CNT variable has 64 observations */
proc sql noprint;
   create table want2 as select distinct org.region ,shoes.product ,shoes.Subsidiary,shoes.stores,
   count(shoes.product) as cnt
	 	from org as org left join 
       shoes as shoes on org.region = shoes.region	    	     
     group by org.region
     order by org.region;
quit;


/*Scenario 3: using DISTINCT at COUNT level getting 64 observations and CNT variable has 8 observations */
proc sql noprint;
   create table want3 as select org.region ,shoes.product ,shoes.Subsidiary,shoes.stores,
   count(distinct(shoes.product)) as cnt
	 	from org as org left join 
       shoes as shoes on org.region = shoes.region	    	     
     group by org.region
     order by org.region;
quit;


/*Scenario 4: using DISTINCT at COUNT level getting 8 observations and CNT variable has 64 observations */
proc sql noprint;
   create table want4 as select distinct org.region ,shoes.product ,shoes.Subsidiary,shoes.stores,
   count(distinct(shoes.product)) as cnt
	 	from org as org left join 
       shoes as shoes on org.region = shoes.region	    	     
     group by org.region
     order by org.region;
quit;

My requirement is NOT TO use DISTINCT at COUNT function but to get the COUNT(CNT) value as 8 since the actual count is 
only 8 in the dataset. If we use distinct at COUNT FUNCTION we will get 8 . But i have customer requirements to use both 
DISTINCT and without DISTINCT but my current issues is not to USE DISTINCT at COUNT function
to get 8 as CNT value though 64 observations are present. Any other alternative/solution for this.

Re: Usage of COUNT function in SQL JOINS with/without DISTINCT keyword

Kurt_Bremser — Fri, 01 May 2020 15:41:39 GMT

Your join will always end up as a cartesian join, because that's how SQL works; when you have M tuples for a key in one dataset and N tuples in the other, the join will give you M*N tuples as result. Unless you prevent that with DISTINCT.

Depending on the actual form of the join, you should contemplate using a data step merge, or prepare your datasets in a way that you'l have a M to 1 join instead of a M to N.

Re: Usage of COUNT function in SQL JOINS with/without DISTINCT keyword

Reeza — Fri, 01 May 2020 15:42:37 GMT

Do you have to use SQL?

I don't think the fix is the count/distinct, it's in the joins most likely - you need to make it a distinct join which usually means adding a join condition. Can you post an example of your org table?

Re: Usage of COUNT function in SQL JOINS with/without DISTINCT keyword

s_lassen — Sat, 02 May 2020 12:24:53 GMT

I think what you want to do is something like this:

proc sql noprint;
   create table want as select distinct org.region ,shoes.product ,shoes.Subsidiary,shoes.stores,shoes.cnt
  	 	from org as org left join 
      (select *,count(*) as cnt from shoes) shoes
   on org.region = shoes.region	    	     
     group by org.region
     order by org.region;
quit;

In other words: do the counting before the join by creating an inner query for shoes.